Switchgear unit for a consumer, especially a motor starter

ABSTRACT

The switchgear unit ( 2 ), especially a motor starter, has a contactor ( 4 ) and a power switch ( 6 ) as short-circuit protection. The additional function of overload protection envisaged for the switchgear unit ( 2 ) is integrated in an overload relay ( 12,16 ) that is configured separately firom the power switch ( 4 ). The components ( 16 ) thereof preferably extend into free areas ( 18,20 ) formed by the arrangement of the contactor ( 4 ) and power switch as standard components on a support ( 8 ). This makes it possible to achieve an economical and space-saving configuration of the switchgear unit ( 2 ).

[0001] This application is the national phase under 35 U.S.C. § 371 ofPCT International Application No. PCT/DE02/01282 which has anInternational filing date of Apr. 8, 2002, which designated the UnitedStates of America and which claims priority on Gerrnan PatentApplication number DE 101 19 458.7 filed Apr. 20, 2001, the entirecontents of which are hereby incorporated herein by reference.

FIELD OF THE INVENTION

[0002] The present invention generally relates to a switchgear unit fora load, in particular a motor starter, having a switching unit forswitching the load during operation, and having the functions of shortcircuit protection and overload protection.

BACKGROUND OF THE INVENTION

[0003] A switchgear unit is generally also referred to as a load feederand is usually arranged in a switchgear cabinet on a standardizedtop-hat rail next to other load feeders. The load feeders arranged in aswitchgear cabinet are assembled in a modular fashion in order to makeit possible to meet the respective requirements. Load feeders of thistype are provided in particular in industrial systems for controllingand switching high currents and voltages. The switchgear unit is used inparticular to drive a three-phase motor. The switchgear unit is in thiscase also referred to as a motor starter.

[0004] The switchgear unit of a motor starter generally has threefunctions for protecting the motor. The first function is that ofswitching the motor during operation, and is performed by a dedicatedstandard unit, usually a so-called contactor. The contactor is designedto repeatedly switch high currents on and off, during operation.Furthermore, in a switchgear unit, the functions of short circuitprotection and overload protection are integrated in a standard unitreferred to as a power breaker. The power breaker isolates the load fromthe power supply system when a short circuit occurs and also when thecurrent is too high. The two standard units are arranged next to oneanother on a common carrier and form the switchgear unit.

[0005] DE 43 35 965 discloses a motor starter having integrated shortcircuit protection and in which a power breaker, an electronic trippingunit and a contactor are arranged one behind the other. The electronictripping unit is integrated together with the power breaker in a commonenclosure. The tripping unit in this case has a release which providesthe thermal overload protection for the motor.

[0006] FR 2 003 575 discloses a contactor having a short circuit releasewhich is provided as an attachment and having an attachment whichcontains a thermal overcurrent release.

[0007] WO 99/23737 discloses a switchgear unit which has a contactor anda power breaker, each as separate units. These units are arranged on asubcarrier in which a printed circuit board with electronics isintegrated. Such electronics make it possible to drive the switchgearunit by way of a bus system. In this case, in particular two bus systemsare provided, that is a data bus for interchanging signals and a powerbus for supplying power. As an alternative to the standard units of thecontactor and the power breaker, an electronic circuit is proposed whichis, however, less suitable for switching very high currents than theelectromechanical units of the contactor and the power breaker, or isvery complex and expensive.

SUMMARY OF THE INVENTION

[0008] An object of the present invention is to specify a cost-effectiveswitchgear unit where design is as simple as possible.

[0009] An object of the present invention is achieved by providing aswitchgear unit, in particular for a motor starter, having the finctionsof switching, short circuit protection and overload protection duringoperation, provision is made for each of these functions to be performedin a separate functional unit. The switching operation is in this casemay be performed by a switching unit, in particular a contactor. Thefunction of short circuit protection may be performed by a powerbreaker, and the function of overload protection may be performed by anoverload relay which is separate from the power breaker.

[0010] The functions of overload protection and short circuit protectionare usually integrated in a conventional power breaker. In order toensure that the finctions of short circuit protection and overloadprotection are reliably performed, the power breaker must bespecifically designed for the switching current envisaged in each case.Switching current is regarded here as the current for which theswitchgear unit is designed. This means that, for example, for theswitching current range between 0 and 25 A, approximately twentyseparate, differently designed power breakers are required. This resultsin considerable cost and requires significant care to be taken whenselecting the appropriate power breaker.

[0011] By separating the functions of short circuit protection andoverload protection, the switchgear unit may be considerably simplified.In particular, the function of overload protection no longer needs to beintegrated in the power breaker, which can primarily be designed for thefunction of short circuit protection. The power breaker as a result hasa much simpler design and is thus more cost-effective, and can also beused over a broad current range. The function of overload protectionperformed in the overload relay is also comparatively simple as a resultof it being separate from the short circuit protection.

[0012] The overload relay may be in the form of an electronic overloadrelay which has, in particular, a current transformer. This currenttransformer is arranged around a conductor to be monitored in the mannerof a current measuring coil, and detects the magnetic field induced bythe conductor through which current is flowing. An electronic evaluationunit connected to the current transformer determines from this thecurrent flowing through the conductor. Based on this principle, theelectronic overload relay can be used for a very broad current range.The electronics determine the current level above which the overloadrelay will trip, and this current level can be almost any desired value.

[0013] In order to allow for a switchgear unit design which is ascost-effective and compact as possible, the switching unit and the powerbreaker may be designed as standard components which are arranged on acarrier so as to form a free space. At least one component of theoverload relay extends into this free space. This makes it possible tokeep the physical space required for the switchgear unit small, whichmeans that there is a small space requirement in the switching cabinetand the installation costs are low.

[0014] Of particular advantage for cost-effective design is the use ofstandard units for the switching unit (contactor) and the power breaker.Such standard units usually have a cutout underneath for mounting themon a top-hat rail, and this cutout forms a free space in which thecomponent preferably engages. In addition, an interspace is usuallyprovided between the contactor and the power breaker and likewiseadvantageously acts as a free space for arranging a component of theoverload relay.

[0015] In an expedient manner, in this case, the current transformer inparticular extends into the free space, since it takes up the mostphysical space owing to its coil structure. A dedicated currenttransformer is provided in the overload relay for each phase of thepower supply system. These current transformers are thus arranged suchthat they are distributed, for example, in the two cutouts or in theinterspace.

[0016] In an expedient manner, for a compact arrangement, the component,which extends into the free spaces, is arranged on the carrier on whichthe contactor and the power breaker are also mounted.

[0017] In a particularly expedient refinement, provision.is made for thecomponents of the overload relay to be arranged on a printed circuitboard on the carrier. The printed circuit board is preferably at thesame time fitted with bus electronics so that the switchgear unit isdesigned for connection to a bus system. By integrating the electronicoverload relay on the printed circuit board, the space requirement isminimized in a particularly efficient manner, and the production costsare kept low. This is because the printed circuit board which is usuallyused for bus electronics nowadays needs only a few additional electronicfunctions for modern switchgear units. Owing to the high degree ofautomation in the production of printed circuit boards, this requiresonly a little additional complexity. However, considerable savings canbe made since, on the one hand, the power breaker can be designed in asimplified fashion without the ftunction of overload protection, and canbe used in the standard way for a broad current range. At the same time,on the other hand, by integrating the electronic overload relay on theprinted circuit board with the current transformers extending into thefree spaces, a very small physical volume is achieved which also keepsthe costs of installing the switchgear unit low.

[0018] Further scope of applicability of the present invention willbecome apparent from the detailed description given hereinafter.However, it should be understood that the detailed description andspecific examples, while indicating exemplary embodiments of the presentinvention, are given by way of illustration only, since various changesand modifications within the spirit and scope of the invention willbecome apparent to those skilled in the art from this detaileddescription.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The present invention will become more fuilly understood from thedetailed description given hereinbelow and the accompanying drawingwhich IS given by way of illustration only, and thus are not limitativeof the present invention, and wherein:

[0020] The single FIGURE illustrates a simplified schematic andperspective illustration of a switchgear unit.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

[0021] The switchgear unit 2 has a contactor 4, in the form of astandard unit, as a switching unit for the function of switching duringoperation. Furthermore, a power breaker 6 is likewise provided as astandard unit for the function of short circuit protection. Thecontactor 4 and the power breaker 6 intended to be arranged on anapproximately L-shaped carrier 8. The carrier 8 is usually intended tobe snapped or pushed onto a top-hat rail in a switchgear cabinet.

[0022] A printed circuit board 10 is integrated in the base of thecarrier 8 and is fitted with a number of electronic components 12 andcontact-making devices 14. In particular, bus electronics are integratedon the printed circuit board 10 such that the switchgear unit 2 can beconnected to a bus system. This bus system is, for example, a signal busfor transmitting signals and/or a power bus for supplying power to theswitchgear unit 2.

[0023] The present invention also provides for the fuinction of overloadprotection to be performed separately from the power breaker 6. For thispurpose, the function of overload protection is performed by anelectronic overload relay which has, in particular, a currenttransformer 16 for each phase conductor of the power supply system.Associated with the electronic overload relay are, furthermore, some ofthe components 12 arranged on the printed circuit board 10. The currenttransformer 16 is in the form of a current measuring coil and serves thepurpose of detecting the magnetic field induced by the phase conductorthrough which current is flowing. The respective current levels aredetermined from the signals from the current transformer 16 by means ofthe components 12.

[0024] Owing to the use of standard units for the contactor 4 and thepower breaker 6, they each have a cutout 18 underneath for arrangingthem on a top-hat rail. When the contactor 4 and the power breakers 6are arranged on the carrier 8, the configuration results in aninterspace 20 being formed between these units. The cutouts 18 and theinterspace 20 form free spaces by virtue of this configuration.

[0025] In order to make expedient use of these free spaces that arepresent, the current transformers 16 extend into these free spaces. Inthe exemplary embodiment, two current transformers 16 are shown whichextend into the cutout 18 in the power breaker 6. As an alternative tothis, the current transformers can also be arranged distributed over thetwo cutouts 18 and the interspace 20, or arranged exclusively in theinterspace 20 or exclusively in the cutout 18 in the contactor 4.

[0026] Owing to the use of the free spaces formed by virtue of theconfiguration, the space requirement for the switchgear unit 2 is keptvery small, overall. This achieves a compact physical volume and keepsthe space requirement in the switchgear cabinet small, and thus theinstallation costs low. In addition, simplification of the power breakeris made possible by integrating the finction of overload protection in aunit which is separate from the power breaker 6, the electronic overloadrelay.

[0027] Exemplary embodiments being thus described, it will be obviousthat the same may be varied in many ways. Such variations are not to beregarded as a departure from the spirit and scope of the presentinvention, and all such modifications as would be obvious to one skilledin the art are intended to be included within the scope of the followingclaims.

1. A switchgear unit, comprising: a switching unit for switching a loadduring operation thereof. the switching unit including short circuitprotection and overload protection functionality, the function of shortcircuit protection being integrated in a power breaker, and that thefunction of overload protection being integrated in a separatefunctional unit in an electronic overload relay which is separate fromthe power breaker.
 2. The switchgear unit as claimed in claim 1, whereinthe overload relay is in the form of an electronic overload relay. 3.The switchgear unit as claimed in claim 1 wherein the switching unit andthe power breaker are in the form of standard components and arearranged on a carrier so as to form a free space, at least one of thecomponents of the overload relay extends into the free space.
 4. Theswitchgear unit as claimed in claim 3, wherein the power breaker and theswitching unit each have a cutout on an underside thereof, the cutoutsbeing for mounting the iower breaker and the switching unit on a top-hatrail, and the component being capable of engaging at least one of thecutouts.
 5. The switchgear unit as claimed in claim 3 4, wherein thepower breaker and the switching unit are arranged next to one another soas to form an interspace. the interspace capable of accommodating thecomponent or a plurality of components.
 6. The switchgear unit asclaimed in claim 3, wherein the overload relay has a current transformerwhich extends into the free space.
 7. The switchgear unit claimed inclaim 3, wherein a component of the overload relay is arranged on thecarrier.
 8. The switchgear unit as claimed in claim 3, wherein thecomponents of the overload relay are arranged on a printed circuit boardon the carrier.
 9. The switchgear unit as claimed in claim 8, whereinthe printed circuit board is fitted with an electronic bus system. 10.The switchgear unit as claimed in claim 1, wherein the load is motorstarter.
 11. The switchgear unit as claimed in claim 2, wherein theswitching unit and the power breaker are in the form of standardcomponents and are arranged on a carrier so as to form a free space, atleast one of the components of the overload relay extends into the freespace.
 12. The switchgear unit as claimed in claim 11, wherein the powerbreaker and the switching unit each have a cutout on an undersidethereof, the cutouts being for mounting the power breaker and theswitching unit on a top-hat rail, and the component being capable ofengaging at least one of the cutouts.
 13. The switchgear unit as claimedin claim 4, wherein the power breaker and the switching unit arearranged next to one another so as to form an interspace, the interspacecapable of accommodating the component or a plurality of components. 14.The switchgear unit as claimed in claim 4, wherein the overload relayhas a current transformer which extends into the free space.
 15. Theswitchgear unit as claimed in claim 5, wherein the overload relay has acurrent transformer which extends into the free space.
 16. Theswitchgear unit claimed in claim 4, wherein a comonent of the overloadrelay is arranged on the carrier.
 17. The switchgear unit claimed inclaim 5, wherein a component of the overload relay is arranged on thecarrier.
 18. The switchgear unit claimed in claim 6, wherein a componentof the overload relay is arranged on the carrier.
 19. The switchgearunit as claimed in claim 4, wherein the components of the overload relayare arranged on a printed circuit board on the carrier.
 20. Theswitchgear unit as claimed in claim 5, wherein the components of theoverload relay are arranged on a printed circuit board on the carrer.21. The switchgear unit as claimed in claim 6, wherein the components ofthe overload relay are arranged on a printed circuit board on thecarrier.
 22. The switchgear unit as claimed in claim 7, wherein thecomponents of the overload relay are arranged on a printed circuit boardon the carrier.
 23. An apparatus, comprising: a mountable power breakerhaving integrated short circuit protection functionality; and overloadprotection circuitry being functionally separate from the power breaker,the overload protection circuitry being position in a free space definedat least in part by the power breaker.
 24. The apparatus according toclaim 23, wherein the over load protection circuitry includes at leastan electronic overload relay.
 25. The apparatus according to claim 23,wherein the free space defined at least in part by the power breaker isdefined by an underside thereof.
 26. The apparatus according to claim23, wherein the power breaker is mounted on a carrier, the power breakerand carrier combination thereby defining a switchgear unit.